DESCRIPTION: In this revised application, the principal investigator states that the intramolecular photocycloaddition reaction of allenes with enoates and enones is a powerful tool for the construction of carbon-carbon bonds in stereochemically complex, polycyclic structures. He reports the he has observed asymmetric induction in the photocyclization and photoaddition reactions of chiral 1,3-disubstituted allenes with an enone in which asymmetry is derived exclusively from the allene fragment. He notes that on the basis of these results, the aims of this proposal are (1) examination of carbocyclic allene-enones and allene-coumarins as substrates for the intramolecular, asymmetric photocycloaddition (2) to develop a detailed understanding of the mechanism of these transformations and develop a paradigm for the prediction of stereochemistry (3) to develop a family of optically active 1,3- disubstituted allenes with removable auxiliary substituents, and (4) the application of the enantioselective allene-enone photoaddition reaction to the synthesis of the biologically active tannin chebulic acid. It is reported that chebulic acid and related tannins exhibit potent antitumerogenic activity by inhibition of calf thymus and human colon adenocarcinoma topoisomerase I.